A federal judge struck down Oregon 's voter-approved ban on same-sex marriage Monday .

`` Because Oregon 's marriage laws discriminate on the basis of sexual orientation without a rational relationship to any legitimate government interest , the laws violate the Equal Protection Clause of the Fourteenth Amendment to the United States Constitution , '' U.S. District Judge Michael McShane said in his ruling .

Oregon voters passed Measure 36 in 2004 , which amended the state 's Constitution to define marriage as between one man and a woman .

In February , the state 's attorney general said she would not defend the ban in court because it would not stand up to a federal constitutional challenge .

`` My decision will not be the final word on this subject , but on this issue of marriage I am struck more by our similarities than our differences . I believe that if we can look for a moment past gender and sexuality , we can see in these plaintiffs nothing more or less than our own families , families who we would expect our Constitution to protect , if not exalt , in equal measure , '' McShane said . `` With discernment we see not shadows lurking in closets or the stereotypes of what was once believed ; rather , we see families committed to the common purpose of love , devotion , and service to the greater community . ''

Same-sex couples camped out in lawn chairs outside a government building in Oregon 's largest county while waiting for the news , then cheered as word of the judge 's decision spread .

Multnomah County began issuing marriage licenses to same-sex couples minutes later , the county said in a statement .

Ben West , one of the plaintiffs who challenged Oregon 's constitutional ban , stood beside his fiance and his son as he told CNN affiliate KGW that he was thrilled by the news .

`` We 're excited . It 's surreal . We 're part of history . Our family is recognized , I mean , I 'm tingling . It 's amazing , '' he said .

`` It means that my son 's family is just as legitimate as the one next door , and that he can grow up proud . ''

At a news conference shortly after the judge 's ruling , activists and attorneys who challenged the amendment celebrated the news .

`` Love won today , '' said Marty Rouse , national field director for the Human Rights Campaign .

Ten years ago , Rouse said , the first same-sex marriages in the United States were celebrated in Massachusetts . And 45 years ago marked another historic moment , he said .

`` Same-sex couples were arrested and sent to jail for dancing together at establishments like the Stonewall Inn , '' he said . `` Today , 45 years later , in 18 states and now including Oregon and the District of Columbia , same-sex couples are dancing together at their own weddings , and they have wedding rings , not handcuffs . History in Oregon . Congratulations . ''

Meanwhile , the National Organization for Marriage , which opposes same-sex marriage , said it had filed a motion with the 9th Circuit Court of Appeals asking judges to block McShane 's ruling .

`` This case is an ugly example of inappropriate cooperation between the Attorney General and the gay marriage lobby , both of whom want to redefine marriage in contravention of the overwhelming decision of the people to define marriage as the union of one man and one woman , '' Brian Brown , the organization 's president , said in a statement . `` The people of Oregon are entitled to a defense of their decision on marriage rather than being abandoned in court . ''

Same-sex marriage now allowed in 18 states

The Oregon ruling continues a near-unbroken string of state and federal court victories nationwide in the past year for supporters of same-sex marriage .

Seventeen other states and the District of Columbia allow same-sex marriage within their borders : California , Connecticut , Delaware , Hawaii , Illinois , Iowa , Maine , Maryland , Massachusetts , Minnesota , New Hampshire , New Jersey , New Mexico , New York , Rhode Island , Vermont , and Washington . Just over a decade ago , there were none .

Earlier this month , judges in Arkansas and Idaho ruled that same-sex marriage bans in those states were unconstitutional . Both decisions are being appealed .

This month also marks the two-year anniversary of President Barack Obama voicing his public support for the first time of same-sex marriage , citing his own `` evolution '' on the issue .

`` At a certain point , I 've just concluded that for me personally it is important for me to go ahead and affirm that I think same-sex couples should be able to get married , '' Obama said at the time .

Groups supporting same-sex marriage applauded the Oregon ruling .

`` The importance of Judge McShane 's decision can not be overemphasized , '' said David Fidanque , executive director of the ACLU of Oregon . `` Our federal Constitution does not allow any state -- or its voters -- to deny same-sex couples equal protection under the law simply because of who they are and who they love . This type of discrimination is wrong , and it 's also unconstitutional . ''

But court battles over the matter are far from over .

About 70 cases dealing with same-sex marriage are now making their way through U.S. courts .

Separate federal appeals courts in recent weeks heard challenges to same-sex marriage bans in Utah , Oklahoma and Virginia . Similar appeals will be heard on current bans in Nevada , Texas , Kentucky , Ohio and Michigan .

Federal judge orders Utah to recognize same-sex marriages

Also Monday , a federal judge said Utah must recognize the marriages of more than 1,200 same-sex couples who obtained marriage licenses earlier this year after a court struck down that state 's same-sex marriage ban .

The U.S. Supreme Court days later issued a stay preventing any more same-sex marriages , but that action left those who got married in the interim in legal limbo .

The judge 's ruling Monday says Utah must give those couples `` all the protections , benefits , and responsibilities given to all marriages under Utah law . ''

While some details of the Oregon and Utah cases are similar , there 's a key difference . In Utah , the state is appealing a judge 's decision to overturn its voter-approved ban of same-sex marriage . Gov. Gary Herbert slammed what he said was a decision by an `` activist federal judge . ''

In Oregon , officials are taking the opposite tack , praising the judge 's ruling overturning their state 's same-sex marriage ban .

`` Now , finally , all Oregonians will have the opportunity to make a legal commitment to the person they love . Every person and every family in Oregon deserves that chance , '' Gov. John Kitzhaber said in a statement . `` Today is a win for love , for families , and for freedom . ''

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Plaintiff : `` It means that my son 's family is just as legitimate as the one next door ''

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Judge : Oregon 's voter-approved same-sex marriage ban is unconstitutional

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Activist after the ruling : `` Love won today ''

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Opponents of same-sex marriage say Oregon abandoned citizens in court